1. Field of the Invention
The present invention relates to systems and methods for the use in a sort processing apparatus which sorts records regarding keys.
2. Description of the Related Art
FIG. 16 shows a conventional key extraction apparatus. It has a main memory 1 and a data input unit 2. A data-write controller 3 generates data-write timing signal 4 for writing data on a data memory 5. The data memory 5 stores some data transferred from the main memory 1. Processor 6 carries out data transfer and/or sort processing. A key memory 7 has some keys extracted from the records stored on the data memory 5 by the micro-processor.
On the main memory 1, there are plural fixed-length records including keys stored at the same locations within each record. FIG. 16 shows an example of the fixed-length records. Each record has seven words and there are some key fields at the same location within each record, for example, one key is located in the second word to the fourth word in a record.
Each record is inputted from the main memory 1 to the data input unit 2 of the key extraction apparatus. The data-write controller 3 provides each memory address for a data-write timing signal 4. The records are written sequentially on the data memory 5 when the timing signal 4 is positive. After writing a record on the data memory 5, the processor 6 extracts and reads a key from the record written on the data memory 5. The processor 6 then writes the key on the key memory 7. Then, the processor 6 sorts the records by using the contents of the key memory 7.
As stated above, the processor is used for extracting keys from the data in the conventional key extraction apparatus. In this conventional system, there are some problems, for example; time to extract some keys can become a part of processor overhead and it thus slows down the processing speed.